Each of a plurality of battery cells within a battery pack has a difference in characteristics from each other and has deterioration differences from each other as a use time of the battery cell is increased. Further, deterioration or a fault diagnosis of the battery may intermittently occur during the use of the battery. Since performance of the battery pack is estimated based on the battery cell having the poorest performance, there is a need to always perform a control to secure the performance of the battery pack by minimally maintaining the difference in the performance of all the battery cells, such as a voltage deviation in the battery cells within the battery pack. Each of the battery cells configuring the battery pack have been used for a charging/discharging operation independent of a difference in performance and deterioration. In this condition, as the use time is increased, the difference in performance and deterioration between the battery cells may be increasingly substantial.
Although a battery management system (BMS) performs a control to reduce the performance deviation of all the battery cells, the difference in deterioration between the battery cells may deviate from a control range of the BMS. In particular, sudden deterioration to the performance of the battery pack may occur due to specific battery cells which are considerably deteriorated. A related apparatus of the related art is illustrated in FIG. 1. Referring to FIG. 1, an apparatus for managing a battery system includes a performance measuring unit 100, a cell switching unit 120, and a controller 130, and the like.
When the measuring voltage of the battery cell 10 is greater or less than a predetermined reference voltage, the controller 130 operates the cell switching unit 120 of the corresponding battery cell 10 to block a connection with another battery cell 10. In other words, under the assumption that the battery has appropriate specifications required by the system, the corresponding battery cell is blocked when control problems occur. Further, only the battery having a problem is blocked and thus the corresponding battery is not used. In addition, only the battery cell having lower performance than the absolute reference performance is blocked.
However, according to the method, since there is a need to always perform a control even when the battery module/cell with a substantial difference in deterioration, the discharge rate of the battery module/cell with substantial deterioration is rapid. As a result, the overall battery pack may need to be replaced. Further, the battery with a problem is blocked, and therefore the remaining performance of the blocked battery cell may not be sufficiently used. Since only the battery with appropriate specifications is mounted, when the corresponding battery cell is blocked, the number of usable battery cells decreases, thereby causing the problem in that the performance and use time of the battery pack may correspondingly decrease.